Transdermal devices for the delivery of biologically active agents have been used for maintaining health and therapeutically treating a wide variety of ailments. For example, analgesics, steroids, etc., have been delivered with such devices. Such transdermal devices include patches in which a biologically active agent is delivered to the body tissue passively without use of an additional energy source. Many such devices have been described, for example, in U.S. Pat. Nos. 3,598,122, 3,598,123, 4,379,454, 4,286,592, 4,314,557, 4,568,343, and U.S. application No. 2003002682, all of which are incorporated herein by reference.
A transdermal patch is typically a small adhesive bandage that contains the drug to be delivered. A simple type of such transdermal patches is an adhesive monolith including a drug-containing reservoir disposed on a backing. The reservoir is typically formed from a pharmaceutically acceptable pressure sensitive adhesive. In some cases, the reservoir can be formed from a non-adhesive material, the skin-contacting surface of which is provided with a thin layer of a suitable adhesive. The rate at which the drug is administered to the patient from these patches can vary due to normal person-to-person and skin site-to-skin site variations in the permeability of skin to the drug.
Sometimes patches can be multilaminate or can include a liquid reservoir layer in the patches. A drug release-rate controlling membrane can be disposed between the drug reservoir and the skin-contacting adhesive. This membrane, by decreasing the release rate of drug from the patch, serves to reduce the effects of variations in skin permeability. However, in one aspect, a controlling membrane interposing between the acrylate nicotine salt reservoir is not needed.
Although the transdermal delivery of therapeutic agents has been the subject of intense research and development for over 30 years, only a relatively small number of drug molecules are suitable for transdermal delivery due to the fact that human skin is an excellent barrier. Various techniques have been explored to enhance the permeation of drug molecules that are not otherwise suitable for transdermal delivery. Of these techniques, chemical enhancement is the most established and is currently employed commercially. Pressure sensitive adhesives, such as acrylic adhesives, are used in many transdermal drug delivery devices as a means of providing intimate contact between the drug delivery device and the skin. The use of enhancers, especially at high concentrations, usually has a significant impact on the properties of pressure sensitive adhesives, such as cohesive strength, adhesive flow, tackiness and adhesion strength. Therefore, pressure sensitive adhesives have to be designed in a way that they can provide the needed performance in the presence of enhancer.
Such a need is especially keen for drugs such as nicotine salt, which is hard to deliver in doses high enough for therapy for some ailments. The NICODERM® patch, as well as other nicotine replacement products, depends on the systemic delivery of the base form of the drug. Such nicotine replacement products are known in the art. Transdermal drug therapy to the delivery of nicotine has been described in the literature, for example, U.S. Pat. Nos. 4,597,961, 4,839,174, 4,908,027, 4,943,435, 5,004,610, 5,135,753, 5,230,896, 5,364,630, 5,508,038, and 6,165,497, herein incorporated by reference in their entireties. However, high concentrations of nicotine in the adhesive layer and in direct contact with the skin may cause irritation or sensitization. Skin irritation is a problem with the topical delivery of certain drugs, see U.S. Pat. Nos. 6,512,010 and 6,203,817. Further, having a high concentration of nicotine in an adhesive causes the adhesive to suffer loss in cohesiveness and adhesiveness. Thus, a transdermal nicotine salt delivery device with less irritation or sensitization, therapeutic flux and drug loading is needed. There continues to be a need for improved delivery of nicotine salt, especially sustained delivery over a period of time.